A contactless method for velocity reconstruction in electrically conducting fluids

A contactless method for three-dimensional velocity reconstruction in elect rically conducting fluids is presented. The method is based on the fact tha t an additional magnetic field is induced if the moving fluid is exposed to a primary magnetic field. By applying the primary magnetic field successiv ely in two different directions and measuring the corresponding induced mag netic fields, the fluid velocity can be reconstructed if some kind of regul arization of the velocity field is used. For a conducting fluid in a sphere , analytical expressions for the connection between spherical harmonics exp ansion coefficients of the induced magnetic fields on one side and of the d efining scalars of the velocity on the other side are derived. For other ge ometries a general method for numerical inversion is proposed.